Demonstration of self-truncated ionization injection for GeV electron beams

Mirzaie, M. and Li, S. and Zeng, M. and Hafz, N. A. M. and Li, G. Y. and Zhu, Q. J. and Liao, H. and Sokollik, T. and Liu, F. and Ma, Y. Y. and Chen, L. M. and Sheng, Z. M. and Zhang, J. (2015) Demonstration of self-truncated ionization injection for GeV electron beams. Scientific Reports, 5. 14659. ISSN 2045-2322

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    Abstract

    Ionization-induced injection mechanism was introduced in 2010 to reduce the laser intensity threshold for controllable electron trapping in laser wakefield accelerators (LWFA). However, usually it generates electron beams with continuous energy spectra. Subsequently, a dual-stage target separating the injection and acceleration processes was regarded as essential to achieve narrow energy-spread electron beams by ionization injection. Recently, we numerically proposed a self-truncation scenario of the ionization injection process based upon overshooting of the laser-focusing in plasma which can reduce the electron injection length down to a few hundred micrometers, leading to accelerated beams with extremely low energy-spread in a single-stage. Here, using 100 TW-class laser pulses we report experimental observations of this injection scenario in centimeter-long plasma leading to the generation of narrow energy-spread GeV electron beams, demonstrating its robustness and scalability. Compared with the self-injection and dual-stage schemes, the self-truncated ionization injection generates higher-quality electron beams at lower intensities and densities, and is therefore promising for practical applications.